Gáspár, Zsolt, Norbert Radics, and Andras Recski. “Rigidity of Square Grids With Holes”. Computer Assisted Methods in Engineering and Science 6, no. 3-4 (December 31, 1999): 329–335. Accessed May 8, 2026. http://cames.ippt.gov.pl/index.php/cames/article/view/1280.